CN113890331A - Mixed type step-down negative resistance converter - Google Patents

Mixed type step-down negative resistance converter Download PDF

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Publication number
CN113890331A
CN113890331A CN202111089933.9A CN202111089933A CN113890331A CN 113890331 A CN113890331 A CN 113890331A CN 202111089933 A CN202111089933 A CN 202111089933A CN 113890331 A CN113890331 A CN 113890331A
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negative resistance
hybrid
switch
negative
conversion module
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CN113890331B (en
Inventor
郑琼林
杨晓峰
王淼
赵治钧
陈茂鲁
游小杰
刘建强
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Beijing Jiaotong University
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Beijing Jiaotong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
    • B60M5/00—Arrangements along running rails or at joints thereof for current conduction or insulation, e.g. safety devices for reducing earth currents
    • B60M5/02—Means for reducing potential difference between rail and adjacent ground
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention belongs to the technical field of electrified rail transit, and relates to a hybrid buck negative resistance converter, which comprises: a step-down conversion module and a mixed negative resistance conversion module. The voltage reduction conversion module converts the voltage of the direct current traction substation into lower intermediate voltage, and then the intermediate voltage is used as the input voltage of the hybrid negative resistance conversion module; the mixed negative resistance transformation module realizes negative impedance output by adjusting the voltage between the two connecting ends of the mixed negative resistance transformation module, and the negative impedance characteristic is obtained by the proportional relation between the voltage between the two connecting ends of the mixed negative resistance transformation module and the current flowing through the two connecting ends. The purpose of the hybrid buck negative resistance converter is: the quantity of power electronic switches is reduced by introducing the mechanical switches, an isolation transformer is not needed, and the train current only has the on-state voltage drop of 1 switch in the negative resistance conversion module, so that the hybrid voltage-reducing negative resistance converter is favorable for thermal design and reduction of the volume of a radiator.

Description

Mixed type step-down negative resistance converter
Technical Field
The invention belongs to the technical field of electrified rail transit, particularly belongs to the technical field of urban rail transit and power electronic converters, relates to a mixed type voltage-reducing negative resistance converter, and particularly relates to a mixed type voltage-reducing negative resistance converter for reducing rail potential and stray current corrosion.
Background
The urban rail transit is approved and favored by various large-scale urban traffic transportation by the characteristics of high-efficiency carrying capacity, convenient commuting experience, extremely low tail gas emission and the like, and is one of effective modes for assisting the sustainable development of cities. However, in urban rail transit, the problem of stray current and rail potential caused by incomplete insulation of running rails from the ground is not negligible, and therefore, attention has been paid to solutions for managing the stray current and the rail potential in urban rail transit.
The existing stray current and track potential treatment measures generally have the problems of high treatment cost, gradually deteriorated treatment effect along with the time lapse, difficult reconstruction on the existing line and the like. Therefore, in the invention patent "a system for reducing the track potential of subway trains" (with the publication number of CN108297741B), a system for actively realizing an approximate zero-impedance branch circuit to shunt the return current of running rails so as to reduce the track potential of the running rails and further reduce the stray current corrosion of an urban rail system is provided. Above-mentioned reduce subway train track potential system includes: negative resistance converter, etc.
Electronic switches are mainly adopted as switching devices in the traditional negative resistance converter, and the advantages of long service life, high reliability and the like of the power electronic switches are mainly considered. The use of a large number of power electronic switches significantly increases the hardware cost, control cost, and heat dissipation cost of the negative-resistance converter.
The polarity of the output voltage of the negative resistance converter is changed according to the direction (traction or braking) of the train current, and when different polarities are output, large current flows through the train. However, the traction energy in the actual urban rail transit is far greater than the braking energy, and the negative resistance converter does not need to frequently switch the polarity of the output voltage; therefore, part of the power electronic switches in the conventional negative resistance converter can be replaced by mechanical switches. Compared with a power electronic switch, the mechanical switch has the advantages of low hardware cost, low switching loss and the like. Therefore, the topological research of the hybrid voltage-reducing negative resistance converter has important significance for reducing the loss of the train under the large current and popularizing 'a system for reducing the track potential of the subway train'.
Disclosure of Invention
Aiming at the characteristic of reducing the large current in a negative resistance converter in a subway train track potential system (with the publication number of CN108297741B), the invention provides a non-isolated hybrid voltage-reducing negative resistance converter, which is briefly described as follows:
1. the mixed type voltage-reducing negative resistance converter consists of a voltage-reducing conversion module and a mixed negative resistance conversion module, wherein the voltage-reducing conversion module converts the voltage of the direct-current traction substation into lower intermediate voltage which is used as the input voltage of the mixed negative resistance conversion module;
2. the hybrid negative resistance conversion module realizes negative impedance output by adjusting the voltage between two connection terminals (i.e. the third connection terminal 63 and the fourth connection terminal 64), and the negative resistance characteristic is realized by an output capacitor C between the two connection terminals of the negative impedance2The proportional relation between the upper voltage and the current flowing through the two connecting ends is obtained;
3. the hybrid step-down negative resistance converter is directly connected to a return point of a running rail from a negative connecting end (namely, a second connecting end 62) and an output connecting end (namely, a third connecting end 63) of the hybrid step-down negative resistance converter which are powered from a direct-current traction substation without transformer isolation;
4. the current only flows through 1 switching device in the mixed negative resistance conversion module.
The concrete technical scheme of the hybrid buck negative resistance converter is as follows:
a hybrid buck negative resistance converter comprising: the circuit comprises a voltage reduction conversion module, a mixed negative resistance conversion module, a first connecting end 61, a second connecting end 62, a third connecting end 63, a fourth connecting end 64, a fifth connecting end 65 and a sixth connecting end 66;
the voltage reduction conversion module is connected with the mixed negative resistance conversion module through a common connecting end;
the public connecting end is: a fifth connection 65 and a sixth connection 66;
the buck conversion module is configured to: converting the voltage of the direct current traction substation into a lower intermediate voltage, and then taking the intermediate voltage as the input voltage of the hybrid negative resistance conversion module;
the hybrid negative resistance transform module includes: input capacitance C1An output capacitor C2Inductor L, switch S1Freewheel diode D, first mechanical switch K1And a second mechanical switch K2；
The input capacitor C1The upper end of which is connected with the fifth connection end 65 and the left end of the switch S;
the input capacitor C1Lower end and sixth connection end 66, first mechanical switch K1Lower end of, output capacitor C2The lower end of the third connecting end 63 is connected with the first connecting end;
one end of the inductor L is connected with the right end of the switch S and the upper end of the freewheeling diode D;
the lower end of the freewheeling diode D and the first mechanical switch K1Upper end of, second mechanical switch K2The lower ends of the two are connected;
the other end of the inductor L and the first mechanical switch K1Right end, second mechanical switch K2The left ends of the two are connected;
second mechanical switch K2Right end and fourth connection end 64, output capacitor C2The upper ends of the two are connected;
the third connection terminal 63 and the fourth connection terminal 64 constitute two connection terminals of negative impedance;
the negative impedance output is realized by adjusting the voltage between the third connection terminal 63 and the fourth connection terminal 64; the negative impedance characteristic is obtained from the voltage between the third connection terminal 63 and the fourth connection terminal 64 in proportion to the current flowing through the third connection terminal 63 and the fourth connection terminal 64.
On the basis of the technical scheme, when the voltage reduction conversion module outputs negative voltage and the mixed negative resistance conversion module inputs negative voltage,
input capacitor C of the hybrid negative resistance conversion module1The upper end of the mixed negative resistance conversion module is a negative electrode end, and the output capacitor C of the mixed negative resistance conversion module2The upper end of the anode is a cathode end; switch S of the hybrid negative resistance conversion module1The right end of the switch S is a positive end, and the left end of the switch S of the hybrid negative resistance conversion module is a negative end; the upper end of a fly-wheel diode D of the hybrid negative resistance conversion module is an anode, and the lower end of the fly-wheel diode D of the hybrid negative resistance conversion module is a cathode; the first mechanical switch K1Is a first contact X1, the first mechanical switch K1Is a second contact X2, the first mechanical switch K1The lower end of the throwing knife is a throwing knife connecting end X3; the second mechanical switch K2The left end of the first mechanical switch K is a first contact Y12Is a second contact Y2, the second mechanical switch K2The right end of the throwing knife is a throwing knife connecting end Y3;
when the buck conversion module outputs positive voltage and the hybrid negative resistance conversion module inputs positive voltage,
input capacitor C of the hybrid negative resistance conversion module1The upper end of the negative resistance conversion module is a positive end, and the output capacitor C of the negative resistance conversion module2The upper end of the anode is a cathode end; switch S of the hybrid negative resistance conversion module1The right end of the negative resistance conversion module is a negative end, and the switch S of the mixed negative resistance conversion module1The left end of the positive electrode is a positive electrode end; the upper end of a fly-wheel diode D of the hybrid negative resistance conversion module is a cathode, and the lower end of the fly-wheel diode D of the hybrid negative resistance conversion module is an anode; the first mechanical switch K1Is a second contact X2, the first mechanical switch K1Is a first contact X1, the first mechanical switch K1The lower end of the throwing knife is a throwing knife connecting end X3; the second mechanical switch K2Is a second contact Y2, the second mechanical switch K2Is a first contact Y1, the second machineSwitch K2The right end of the throwing knife is a throwing knife connecting end Y3.
On the basis of the technical scheme, when the hybrid negative resistance conversion module inputs negative voltage and a train is in a traction working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1The first contact X1 is connected with the throwing knife connecting end X3, and the second mechanical switch K2The first contact Y1 is connected with the throwing knife connecting end Y3; the hybrid buck negative-resistance converter outputs a positive polarity specified amplitude voltage between the third connection terminal 63 and the fourth connection terminal 64 thereof;
when the hybrid negative resistance conversion module inputs negative voltage and the train is in the regenerative braking working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1A second contact X2 connected to the throwing-knife connecting end X3, and a second mechanical switch K2The second contact Y2 is connected with the throwing knife connecting end Y3; the hybrid step-down negative resistance converter outputs a negative polarity specified amplitude voltage between the third connection terminal 63 and the fourth connection terminal 64 thereof.
When the hybrid negative resistance conversion module inputs positive voltage and the train is in traction working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1The first contact X1 is connected with the throwing knife connecting end X3, and the second mechanical switch K2The first contact Y1 is connected with the throwing knife connecting end Y3; the hybrid buck negative-resistance converter outputs a positive polarity specified amplitude voltage between the third connection terminal 63 and the fourth connection terminal 64 thereof;
when the hybrid negative resistance conversion module inputs positive voltage and the train is in the regenerative braking working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1A second contact X2 connected to the throwing-knife connecting end X3, and a second mechanical switch K2The second contact Y2 is connected with the throwing knife connecting end Y3; the hybrid step-down negative resistance converter outputs a negative polarity specified amplitude voltage between the third connection terminal 63 and the fourth connection terminal 64 thereof.
On the basis of the technical scheme, when the buck conversion module outputs negative voltage,
the voltage reduction conversion moduleThe method comprises the following steps: input capacitance C1An output capacitor C2A switch S, an inductor L and a freewheeling diode D;
the input capacitor C1Negative terminal and second connection terminal 62, one terminal of inductor L, input capacitor C2The positive terminal and the sixth connecting terminal 66 are connected;
the input capacitor C1The positive terminal of the switch is connected with the first connecting terminal 61 and the positive terminal of the switch S;
the negative end of the switch S is connected with the other end of the inductor L and the cathode end of the freewheeling diode D;
the anode end of the freewheeling diode D, the fifth connecting end 65 and the output capacitor C2The negative ends of the anode and the cathode are connected;
the switch S is pulse modulated according to the input voltage characteristics.
When the buck converter module outputs a positive voltage,
the buck conversion module comprises: input capacitance C1An output capacitor C2A switch S, an inductor L and a freewheeling diode D;
the input capacitor C1And the negative terminal and the second connection terminal 62, the anode terminal of the freewheeling diode D, the output capacitor C2The negative end and the sixth connecting end 66 are connected;
the input capacitor C1The positive terminal of the switch is connected with the first connecting terminal 61 and the positive terminal of the switch S;
the negative end of the switch S is connected with one end of the inductor L and the cathode end of the freewheeling diode D;
the other end of the inductor L, the fifth connection terminal 65 and the input capacitor C2The positive terminals are all connected;
the switch S is pulse modulated according to the input voltage characteristics.
On the basis of the above technical solution, the hybrid negative resistance conversion module further includes: an RC absorption circuit;
the RC absorption circuit includes: two absorption resistors Rs1Two absorption resistors Rs2Two absorption capacitors Cs1And two absorption capacitors Cs2；
The first mechanical switch K1First contact X1 and absorption resistor Rs1Is connected to the absorption resistor Rs1Another terminal of (1) and an absorption capacitor Cs1Is connected to the absorption capacitor Cs1Another terminal of (1) and an absorption capacitor Cs2One end of, the first mechanical switch K1The throwing knives are connected with X3, and the absorption capacitor Cs2Another end of (1) and an absorption resistor Rs2Is connected to the absorption resistor Rs2The other end of (2) and the first mechanical switch K1To the second contact X2;
the second mechanical switch K2And a first contact Y1 with a further absorption resistor Rs1Is connected to one end of the other absorption resistor Rs1The other end of which is connected to another absorption capacitor Cs1Is connected to one end of the further absorption capacitor Cs1The other end of which is connected to another absorption capacitor Cs2One end of, a second mechanical switch K2The throwing knives are connected with the connecting ends Y3, and the other absorbing capacitor Cs2With the other end of the other absorption resistor Rs2Is connected to one end of the other absorption resistor Rs2And the other end of the first mechanical switch K2Is connected to the second contact Y2.
On the basis of the above technical solution, when the hybrid negative resistance conversion module inputs a negative voltage, the hybrid negative resistance conversion module further includes: two diodes Ds1And two diodes Ds2；
At the two absorption resistors Rs1Are respectively connected with a diode D in parallels1And a diode Ds1Anode terminal and first mechanical switch K1Is connected to a first contact X1, and a further diode Ds1Anode terminal and second mechanical switch K2Is connected with the first contact Y1;
at the two absorption resistors Rs2Are respectively connected with a diode D in parallels2And a diode Ds2The cathode terminal and the first mechanical switch K1Is connected to a second contact X2, and a further diode Ds2Cathode terminal ofAnd a second mechanical switch K2To second contact Y2;
when the hybrid negative resistance conversion module inputs a positive voltage, the hybrid negative resistance conversion module further includes: two diodes Ds1And two diodes Ds2；
At the two absorption resistors Rs1Are respectively connected with a diode D in parallels1And a diode Ds1The cathode terminal and the first mechanical switch K1Is connected to a first contact X1, and a further diode Ds1Cathode terminal and second mechanical switch K2Is connected with the first contact Y1;
at the two absorption resistors Rs2Are respectively connected with a diode D in parallels2And a diode Ds2Anode terminal and first mechanical switch K1Is connected to a second contact X2, and a further diode Ds2Anode terminal and second mechanical switch K2To second contact Y2;
the two diodes Ds1Two diodes Ds2And the RC absorption circuit forms an RCD absorption circuit.
On the basis of the above technical solution, the hybrid negative resistance conversion module further includes: an RC absorption circuit;
the RC absorption circuit includes: two absorption resistors RsTwo absorption capacitors Cs1And two absorption capacitors Cs2；
The first mechanical switch K1First contact X1 and absorption capacitor Cs1Is connected to the absorption capacitor Cs1Another terminal of (1) and an absorption capacitor Cs2One end of (1), absorption resistance RsAre all connected, the absorption resistor RsThe other end of (2) and the first mechanical switch K1Is connected with the throwing knife connecting end X3, and the absorption capacitor Cs2The other end of (2) and the first mechanical switch K1To the second contact X2;
the second mechanical switch K2First contact Y1 and a further absorption capacitor Cs1Is connected to one end of the further absorption capacitor Cs1The other end of the first suction pipe and the other suction pipeCapacitor Cs2One end of (1), the other absorption resistor RsAre all connected, the other absorption resistor RsAnd the other end of the first mechanical switch K2Is connected to the throw-blade connection terminal Y3, and the other absorption capacitor Cs2And the other end of the first mechanical switch K2Is connected to the second contact Y2.
On the basis of the technical scheme, the switch S1And the switch S are power electronic switches with anti-parallel diodes;
the power electronic switch is as follows: a turn-off switching device or a combination of turn-off switching devices;
the turn-off switching device is: IGBT, MOSFET, SiC-MOSFET or IGCT.
The anti-parallel diode and the freewheeling diode D are fast recovery diodes matched with the turn-off switching device;
the first mechanical switch K1And a second mechanical switch K2All are as follows: a mechanical contact switch;
the mechanical contact switch is as follows: a single-pole double-throw mechanical contact switch (also called a single-pole double-throw mechanical switch).
A reduce subway train track potential system of using above-mentioned mixed type step-down negative resistance converter places mixed type step-down negative resistance converter in drawing power supply system, constitutes and reduces subway train track potential system, reduce subway train track potential system includes: the system comprises two mixed type voltage-reducing negative resistance converters, a plurality of switch units, a contact network 2, a traveling rail 3 and a return line 5;
the two mixed type voltage reduction negative resistance converters are respectively as follows: a first hybrid buck negative resistance converter 6a and a hybrid buck negative resistance converter 6 b;
the switch units are respectively as follows: switch unit 7a, switch units 7b, …, switch unit 7 x;
each of the switching units includes: a switching cell first terminal 71 and a switching cell second terminal 72;
the first connection end 61 of the first hybrid buck negative resistance converter 6a is connected with the traction network connection end 11 of the direct current traction substation 1a, and the first connection end 61 of the second hybrid buck negative resistance converter 6b is connected with the traction network connection end 11 of the direct current traction substation 1 b;
the second connecting end 62 of the first hybrid buck negative resistance converter 6a is connected with the traveling rail connecting end 12 of the direct current traction substation 1a, and the second connecting end 62 of the second hybrid buck negative resistance converter 6b is connected with the traveling rail connecting end 12 of the direct current traction substation 1 b;
the third connecting end 63 of the first hybrid buck negative resistance converter 6a is also connected with the traveling rail connecting end 12 of the direct-current traction substation 1a, and the third connecting end 63 of the second hybrid buck negative resistance converter 6b is also connected with the traveling rail connecting end 12 of the direct-current traction substation 1 b;
the fourth connection end 64 of the first hybrid buck negative resistance converter 6a is connected with the return line 5, and the fourth connection end 64 of the second hybrid buck negative resistance converter 6b is also connected with the return line 5;
the traveling rail connecting end 12 of the direct current traction substation 1a and the traveling rail connecting end 12 of the direct current traction substation 1b are both connected with the traveling rail 3;
the traction network connecting end 11 of the direct current traction substation 1a and the traction network connecting end 11 of the direct current traction substation 1b are both connected with the contact network 2;
the switch unit first terminals 71 are connected to the running rails 3, and the switch unit second terminals 72 are connected to the return lines 5.
On the basis of the technical scheme, in an urban rail transit system, the hybrid buck negative resistance converter, a return line 5 and a plurality of switch units form a zero-resistance return system; through the matching of the switch unit and the adjustment of the impedance of the hybrid voltage-reducing negative resistance converter, the output impedance of the hybrid voltage-reducing negative resistance converter is offset with the impedance of the return line 5 flowing through the current, so that a zero-resistance loop is constructed to transfer the train return current.
The invention has the following beneficial effects:
1. the hybrid voltage-reducing negative resistance converter directly obtains the input voltage from the direct-current traction substation, and other direct-current power supplies isolated from the traction substation are not needed to obtain the input voltage, so that the manufacturing cost is reduced;
2. the hybrid voltage-reducing negative resistance converter directly obtains input voltage from a direct current traction substation, and the output voltage and the input voltage are not required to be isolated, so that an isolation transformer is omitted, the cost and the volume of the negative resistance converter are reduced, and the loss is also reduced;
3. the mixed negative resistance conversion module of the mixed buck negative resistance converter only flows through 1 power electronic switch or a fly-wheel diode matched with the power electronic switch from the middle input voltage to the output voltage, so that the on-state loss of large current of the mixed negative resistance conversion module in a power electronic device is greatly reduced, and the heat design of the mixed buck negative resistance converter and the reduction of the volume of a radiator are facilitated.
Drawings
The invention has the following drawings:
FIG. 1 is a schematic diagram of a typical applied connection structure of a negative resistance converter in the prior art;
fig. 2 is a schematic diagram of a main circuit structure of a hybrid negative resistance conversion module in the hybrid buck negative resistance converter according to the present invention when a negative voltage is input;
fig. 3 is a schematic circuit diagram of a hybrid negative resistance conversion module in the hybrid buck negative resistance converter according to the present invention when a positive voltage is input;
FIG. 4 is a schematic circuit diagram of a buck conversion module of the hybrid buck negative resistance converter of the present invention when outputting a negative voltage;
fig. 5 is a schematic circuit diagram of the buck conversion module in the hybrid buck negative resistance converter of the present invention when outputting a positive voltage;
fig. 6 is a schematic diagram of a RC absorption circuit structure of the single-pole double-throw mechanical switch according to the present invention;
fig. 7 is a schematic diagram of an RC absorption circuit structure of the single-pole double-throw mechanical switch according to the present invention;
fig. 8 is a schematic diagram of a first RCD snubber circuit of the single-pole double-throw mechanical switch according to the present invention;
fig. 9 is a schematic diagram of an RCD snubber circuit configuration of the single-pole double-throw mechanical switch of the present invention;
FIG. 10 is a schematic diagram of a circuit structure of a hybrid buck negative resistance converter applied to a system for reducing the rail potential of a subway train according to the present invention;
FIG. 11 is a schematic diagram of a first power electronic switch type of the hybrid buck negative converter of the present invention;
FIG. 12 is a schematic diagram of a second type of power electronic switch in the hybrid buck negative converter of the present invention;
fig. 13 is a schematic diagram of a third type of power electronic switch in the hybrid buck negative-resistance converter of the present invention.
Detailed Description
To describe the present invention more specifically, the technical solutions of the present invention will be described in more detail below with reference to the accompanying drawings and the embodiments. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.
As shown in fig. 1, which is a diagram (a) of fig. 3 in the invention patent "a system for reducing the track potential of a subway train" (with publication number: CN108297741B), a negative resistance converter is applied to an existing dc traction power supply system for subway rail transit, and the system for reducing the track potential of the subway train comprises: a return line 5, a negative resistance converter 6 (i.e., negative resistance converter 6a and negative resistance converter 6b in fig. 1), and a switching unit 7 (i.e., switching unit 7a, switching units 7b, …, switching unit 7x in fig. 1);
the connection mode of the negative resistance converter 6a and the negative resistance converter 6b in the system for reducing the rail potential of the subway train is as follows: the first connecting end 61 of the negative resistance converter 6a is connected with the traveling rail 3, and the first connecting end 61 of the negative resistance converter 6b is also connected with the traveling rail 3; the second connection 62 of the negative impedance converter 6a is connected to the return line 5, and the second connection 62 of the negative impedance converter 6b is also connected to the return line 5; the negative resistance characteristic is obtained by the proportional relation between the voltage on the output capacitor between the first connection end 61 and the second connection end 62 and the current flowing through the two connection ends (i.e. the first connection end 61 and the second connection end 62).
As shown in fig. 2, a schematic diagram of a main circuit structure of a hybrid negative resistance converter module of the hybrid buck negative resistance converter of the present invention when a negative voltage is input, where the hybrid buck negative resistance converter is formed by cascading the buck converter module and the hybrid negative resistance converter module, and a terminal of the hybrid buck negative resistance converter 6 mainly includes: a first connection end 61, a second connection end 62, a third connection end 63, a fourth connection end 64, a fifth connection end 65 and a sixth connection end 66;
the fifth connection terminal 65 and the sixth connection terminal 66 are common connection terminals of the buck conversion module and the hybrid negative resistance conversion module, and constitute an output port of the buck conversion module and an input port of the hybrid negative resistance conversion module.
In addition, two typical cases can be further classified according to the difference in voltage polarity between the fifth connection terminal 65 and the sixth connection terminal 66:
the first condition is as follows: the voltage reduction conversion module outputs negative voltage and corresponds to the hybrid negative resistance conversion module inputs negative voltage;
case two: the voltage reduction conversion module outputs positive voltage and corresponds to the mixed negative resistance conversion module which inputs positive voltage.
In the two cases, the circuit connection and the operation principle in the typical schemes of the hybrid negative resistance conversion module and the buck conversion module will be discussed in detail below.
As shown in fig. 2 and 10, when a negative voltage is input to the hybrid negative resistance conversion module of the hybrid buck negative resistance converter, the main circuit connection mode is as follows:
input capacitor C of hybrid negative resistance conversion module1Is connected to the fifth connection 65 and inputs the capacitor C1Is connected to the sixth connection terminal 66 and simultaneously inputs the capacitor C1The positive terminal of (a) is used as a third connection terminal 63 of the hybrid buck negative-resistance converter; output capacitor C2Is connected with the third connecting end 63, and outputs a capacitor C2As a fourth connection 64 of the hybrid buck negative converter, the negative terminal of (C) is input to the capacitor (C)1The negative pole end of the switch is sequentially connected with a power electronic switch S in series1Inductor L and second mechanical switch K2First contact Y1 and second mechanical switch K2Is connected with the throwing knife after being connected with the end Y3 and is connected with the output capacitor C2The negative ends of the anode and the cathode are connected; anode of freewheeling diode DConnected to the junction of the positive pole of the power electronic switch S and the inductor L, and the cathode of the freewheeling diode D is connected to the first mechanical switch K1First contact X1, first mechanical switch K1First contact X1 and second mechanical switch K2To the second contact Y2; first mechanical switch K1Second contact X2 and second mechanical switch K2Is connected to the first contact Y1, the first mechanical switch K1The throwing knife connecting end X3 is connected with the third connecting end 63 of the hybrid voltage-reducing negative resistance converter, and the second mechanical switch K2The throwing blade connection end Y3 is connected with the fourth connection end 64 of the hybrid buck negative resistance converter.
The polarity of the output voltage of the hybrid voltage-reducing negative resistance converter is changed according to the direction (traction or braking) of the train current; at this time, the working principle of the hybrid negative resistance conversion module when inputting the negative voltage is as follows:
when the train is in the traction condition, the train traction current flows in from the fourth connection end 64 and flows out from the third connection end 63, namely flows from the return line 5 to the running rail connection end 12 of the direct current traction substation 1 (namely, the direct current traction substation 1a and the direct current traction substation 1b in fig. 10) through the hybrid step-down negative resistance converter, in order to enable the hybrid step-down negative resistance converter to output the positive specified amplitude voltage between the third connection end 63 and the fourth connection end 64 thereof so as to output the negative impedance in combination with the train traction current equivalent, the first mechanical switch K1The first contact X1 is connected with the throwing knife connecting end X3, and the second mechanical switch K2The first contact Y1 is connected with the throwing knife connecting end Y3; at the moment, the power electronic switch S carries out pulse modulation according to the negative resistance characteristic;
when the train is in the regenerative braking condition, the train traction current flows in from the third connection end 63 and flows out from the fourth connection end 64, namely, the train traction current flows from the running rail connection end 12 of the direct current traction substation 1 (namely, the direct current traction substation 1a and the direct current traction substation 1b in fig. 10) to the return line 5 through the hybrid step-down negative resistance converter, in order to enable the hybrid step-down negative resistance converter to output a voltage with a specified amplitude of negative polarity between the third connection end 63 and the fourth connection end 64 thereof so as to equivalently output negative impedance by combining the train traction current, the first mechanical switch K1A second contact X2 connected to the throwing-knife connecting end X3, and a second mechanical switch K2The second contact Y2 is connected with the throwing knife connecting end Y3; at this time, the power electronic switch S is pulse modulated according to the negative resistance characteristic.
As shown in fig. 3 and 10, when a positive voltage is input to the hybrid negative resistance conversion module of the hybrid buck negative resistance converter, the circuit connection mode is as follows:
input capacitor C of hybrid negative resistance conversion module1Is connected to the fifth connection terminal 65, and an input capacitor C1Is connected to the sixth connection 66 and is fed with the capacitor C1The negative terminal of (a) is used as a third connection terminal 63 of the hybrid buck negative resistance converter; output capacitor C2Is connected with the third connecting end 63, and outputs a capacitor C2As a fourth connection 64 of the hybrid buck negative converter, the negative terminal of (C) is input to the capacitor (C)1The positive terminal of the switch is sequentially connected with a power electronic switch S in series1Inductor L and second mechanical switch K2Second contact Y2 and second mechanical switch K2Is connected with the throwing knife after being connected with the end Y3 and is connected with the output capacitor C2The negative ends of the anode and the cathode are connected; the cathode of the freewheeling diode D is connected to the connection point of the negative pole of the power electronic switch S and the inductor L, and the anode of the freewheeling diode D is connected to the first mechanical switch K1Second contact X2, first mechanical switch K1First contact X1 and second mechanical switch K2Is connected to the second contact Y2, the first mechanical switch K1Second contact X2 and second mechanical switch K2Is connected to the first contact Y1, the first mechanical switch K1The throwing knife connecting end X3 is connected with the third connecting end 63 of the hybrid voltage-reducing negative resistance converter, and the second mechanical switch K2The throwing blade connection end Y3 is connected with the fourth connection end 64 of the hybrid buck negative resistance converter.
At this time, the working principle of the hybrid negative resistance conversion module when the positive voltage is input is as follows:
when the train is in the traction working condition, the train traction current flows in from the fourth connecting end 64 and flows out from the third connecting end 63, namely flows from the return line 5 to the direct current traction substation 1 (namely, flows to the direct current traction substation through the hybrid buck negative resistance converterThe first mechanical switch K in fig. 10 is used for the rail connecting terminal 12 of the dc traction substation 1a and the dc traction substation 1b) to make the hybrid buck negative-resistance converter output a positive specified-amplitude voltage between the third connecting terminal 63 and the fourth connecting terminal 64 thereof for equivalently outputting a negative impedance in combination with a train traction current1The first contact X1 is connected with the throwing knife connecting end X3, and the second mechanical switch K2The first contact Y1 is connected with the throwing knife connecting end Y3; at the moment, the power electronic switch S carries out pulse modulation according to the negative resistance characteristic;
when the train is in the regenerative braking condition, the train traction current flows in from the third connection end 63 and flows out from the fourth connection end 64, namely, the train traction current flows from the running rail connection end 12 of the direct current traction substation 1 (namely, the direct current traction substation 1a and the direct current traction substation 1b in fig. 10) to the return line 5 through the hybrid step-down negative resistance converter, in order to enable the hybrid step-down negative resistance converter to output a voltage with a specified amplitude of negative polarity between the third connection end 63 and the fourth connection end 64 thereof so as to equivalently output negative impedance by combining the train traction current, the first mechanical switch K1A second contact X2 connected to the throwing-knife connecting end X3, and a second mechanical switch K2The second contact Y2 is connected with the throwing knife connecting end Y3; at this time, the power electronic switch S is pulse modulated according to the negative resistance characteristic.
When the hybrid negative resistance conversion module of the hybrid buck negative resistance converter inputs a negative voltage, the buck conversion module needs to output the negative voltage. At this time, the buck conversion module may adopt a typical scheme one as shown in fig. 4, and its main circuit connection mode is:
input capacitor C of buck conversion module of hybrid buck negative resistance converter1Is connected to the first connection terminal 61, inputs the capacitance C1Is connected to the second connection 62 and inputs the capacitor C2Is connected to the fifth connection 65 and inputs the capacitor C2The first connection end 61 of the hybrid buck negative resistance converter is connected with the fifth connection end 65 of the hybrid buck negative resistance converter after being sequentially connected with the switch S and the freewheeling diode D in series, and one end of the inductor L, the negative end of the switch S and the freewheeling diode DThe cathode end of the anode is connected; input capacitance C1Is connected to the other end of the inductor L and then to the output capacitor C2The positive terminal of (1);
at this time, the main working principle of the buck conversion module is as follows: in order to enable the buck conversion module to output a negative polarity specified amplitude voltage between the fifth connection end 65 and the sixth connection end 66 of the buck conversion module, the negative polarity specified amplitude voltage is supplied to the hybrid negative resistance conversion module to realize a corresponding negative resistance conversion function; at this time, the switch S performs pulse modulation according to the input voltage characteristic.
When the hybrid negative resistance conversion module of the hybrid buck negative resistance converter inputs a positive voltage, the buck conversion module needs to output the positive voltage. At this time, the buck conversion module may adopt a typical scheme two as shown in fig. 5, and a main circuit connection mode thereof is as follows:
input capacitor C of buck conversion module of hybrid buck negative resistance converter1Is connected to the first connection terminal 61, inputs the capacitance C1Is connected to the second connection 62 and inputs the capacitor C2Is connected to the fifth connection terminal 65, and an input capacitor C2The first connection end 61 of the hybrid buck negative resistance converter is connected to the fifth connection end 65 of the hybrid buck negative resistance converter after being sequentially connected with the switch S and the inductor L in series, the cathode end of the freewheeling diode D is connected with the cathode end of the switch S, and the input capacitor C is connected with the input capacitor C1Is connected to the output capacitor C after being connected with the anode end of the freewheeling diode D2The positive terminal of (1);
at this time, the main working principle of the buck conversion module is as follows: in order to enable the buck conversion module to output a positive specified amplitude voltage between the fifth connection terminal 65 and the sixth connection terminal 66 of the buck conversion module, the positive specified amplitude voltage is supplied to the hybrid negative resistance conversion module to realize a corresponding negative resistance conversion function; at this time, the switch S performs pulse modulation according to the input voltage characteristic.
As is known, the energy required by train traction in urban rail transit is far larger than the energy fed back by train braking. When the train is in a traction working condition, the train traction current flows to a traveling rail connecting end 12 of the direct current traction substation 1 through the mixed type voltage reduction negative resistance converter by a return line 5; the switching loss of the hybrid negative resistance conversion module with negative voltage input is greatly lower than that of the hybrid negative resistance conversion module with positive voltage input under the same load current. Therefore, the hybrid negative resistance conversion module with negative voltage input and the matched buck conversion module are taken as the preferable scheme of the hybrid buck negative resistance converter.
As shown in fig. 6-9, which are schematic diagrams of absorption circuits of single-pole double-throw mechanical switches in the hybrid negative resistance conversion module of the present invention, RC absorption circuits as shown in fig. 6 and 7 can be adopted:
in fig. 6, the first contact of the single pole double throw mechanical switch (i.e., the first mechanical switch K)1First contact X1 or second mechanical switch K in2The first contact Y1) through the absorption resistor Rs1And an absorption capacitor Cs1Connection to the throwing blade (i.e. first mechanical switch K)1The throwing knife connecting end X3 or a second mechanical switch K2The middle throwing knife connecting end Y3); and the second contact of the single-pole double-throw mechanical switch (i.e. the first mechanical switch K)1Second contact X2 or second mechanical switch K2Second contact Y2) through the absorption resistor Rs2And an absorption capacitor Cs2Is connected with the connecting end of the throwing knife.
In fig. 7, the first contact of the single pole double throw mechanical switch is via the absorption capacitor Cs1The second contact passes through an absorption capacitor Cs2Are all equal to the absorption resistance RsAre connected to the same side of the resistor R, and absorb the resistance RsThe other side of the throwing blade is connected with the connecting end of the throwing knife; at this time, the first contact and the second contact share the same absorption resistor RsSo as to reduce the installation volume and cost.
In addition, an RCD absorption circuit as shown in fig. 8 and 9 may be adopted, that is, a diode D is additionally added on the basis of fig. 6s1And a diode Ds2And a diode Ds1Is connected in parallel with the absorption resistor Rs1Two-terminal, diode Ds2Is connected in parallel with the absorption resistor Rs2Two ends.
In fig. 8, the first contact of the single-pole double-throw mechanical switch is connected with a diode Ds1Is connected to the anode terminal of the diode D, and the second contact is connected to the diode Ds2The cathode end of the anode is connected with the cathode,to adapt to the situation that the hybrid negative resistance conversion module is used as an input negative voltage.
In fig. 9, the first contact of the single-pole double-throw mechanical switch is connected with a diode Ds1Is connected to the cathode terminal of the diode D, and the second contact is connected to the diode Ds2The anode terminal of the hybrid negative resistance conversion module is connected to adapt to the situation that the hybrid negative resistance conversion module inputs positive voltage.
The typical scheme of the invention which is applied to the invention patent of a system for reducing the track potential of a subway train (with the publication number of CN108297741B) is shown in figure 10. The hybrid buck negative-resistance converter 6 (i.e., the hybrid buck negative-resistance converter 6a and the hybrid buck negative-resistance converter 6b in fig. 7) has 4 terminals externally led out: a first connection end 61, a second connection end 62, a third connection end 63 and a fourth connection end 64; the first connection end 61 is connected to the traction network connection end 11 of the direct current traction substation 1 (i.e., the positive end of the direct current traction substation 1), the second connection end 62 is connected to the running rail connection end 12 of the traction substation 1, the third connection end 63 is connected to the running rail connection end 12 of the traction substation 1, the fourth connection end 64 is connected to the return line 5, and the alternating current ends 13 are disposed on the direct current traction substation 1a and the direct current traction substation 1 b.
As shown in fig. 11-13, in the low-loss negative-resistance converter (i.e. the hybrid buck negative-resistance converter), the power electronic switch is a turn-off switching device such as an IGBT (as shown in fig. 11), a MOSFET (as shown in fig. 12), a SiC-MOSFET (as shown in fig. 12) or an IGCT (as shown in fig. 13) or a combination of these switching devices, the anti-parallel diode or the freewheeling diode is a fast recovery diode matched with the power electronic switching device, and the single-pole double-throw mechanical switch is a mechanical contact switch.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Those not described in detail in this specification are within the knowledge of those skilled in the art.

Claims (10)

1. A hybrid buck negative resistance converter, comprising: the circuit comprises a voltage reduction conversion module, a mixed negative resistance conversion module, a first connecting end (61), a second connecting end (62), a third connecting end (63), a fourth connecting end (64), a fifth connecting end (65) and a sixth connecting end (66);
the voltage reduction conversion module is connected with the mixed negative resistance conversion module through a common connecting end;
the public connecting end is: a fifth connection (65) and a sixth connection (66);
the buck conversion module is configured to: converting the voltage of the direct-current traction substation into an intermediate voltage, and then taking the intermediate voltage as the input voltage of the hybrid negative resistance conversion module;
the hybrid negative resistance transform module includes: input capacitance C1An output capacitor C2Inductor L, switch S1Freewheel diode D, first mechanical switch K1And a second mechanical switch K2；
The input capacitor C1Upper end and fifth connecting end (65), switch S1The left ends of the two are connected;
the input capacitor C1Lower end and sixth connecting end (66), first mechanical switch K1Lower end of, output capacitor C2The lower end of the first connecting end (63) and the third connecting end are connected;
one end of the inductor L and the switch S1The right end of the fly-wheel diode D is connected with the upper end of the fly-wheel diode D;
the lower end of the freewheeling diode D and the first mechanical switch K1Upper end of, second mechanical switch K2The lower ends of the two are connected;
the other end of the inductor L and the first mechanical switch K1Right end, second mechanical switch K2The left ends of the two are connected;
second mechanical switch K2Right end and fourth connection end (64), output capacitor C2The upper ends of the two are connected;
the third connecting end (63) and the fourth connecting end (64) form two connecting ends of negative impedance;
the negative impedance output is realized by adjusting the voltage between the third connecting terminal (63) and the fourth connecting terminal (64); the negative impedance characteristic is obtained from the voltage between the third connection terminal (63) and the fourth connection terminal (64) and the current flowing through the third connection terminal (63) and the fourth connection terminal (64) in a proportional relationship.
2. The hybrid buck negative resistance converter of claim 1, wherein: when the voltage reduction conversion module outputs negative voltage and the hybrid negative resistance conversion module inputs negative voltage,
input capacitor C of the hybrid negative resistance conversion module1The upper end of the mixed negative resistance conversion module is a negative electrode end, and the output capacitor C of the mixed negative resistance conversion module2The upper end of the anode is a cathode end; switch S of the hybrid negative resistance conversion module1The right end of the negative resistance conversion module is a positive end, and the switch S of the negative resistance conversion module1The left end of (a) is a negative end; the upper end of a fly-wheel diode D of the hybrid negative resistance conversion module is an anode, and the lower end of the fly-wheel diode D of the hybrid negative resistance conversion module is a cathode; the first mechanical switch K1Is a first contact X1, the first mechanical switch K1Is a second contact X2, the first mechanical switch K1The lower end of the throwing knife is a throwing knife connecting end X3; the second mechanical switch K2The left end of the first mechanical switch K is a first contact Y12Is a second contact Y2, the second mechanical switch K2The right end of the throwing knife is a throwing knife connecting end Y3;
when the buck conversion module outputs positive voltage and the hybrid negative resistance conversion module inputs positive voltage,
input capacitor C of the hybrid negative resistance conversion module1The upper end of the negative resistance conversion module is a positive end, and the output capacitor C of the negative resistance conversion module2The upper end of the anode is a cathode end; switch S of the hybrid negative resistance conversion module1The right end of the negative resistance conversion module is a negative end, and the switch S of the mixed negative resistance conversion module1The left end of the positive electrode is a positive electrode end; the upper end of a fly-wheel diode D of the hybrid negative resistance conversion module is a cathodeThe lower end of a fly-wheel diode D of the hybrid negative resistance conversion module is an anode; the first mechanical switch K1Is a second contact X2, the first mechanical switch K1Is a first contact X1, the first mechanical switch K1The lower end of the throwing knife is a throwing knife connecting end X3; the second mechanical switch K2Is a second contact Y2, the second mechanical switch K2Is a first contact Y1, and the second mechanical switch K2The right end of the throwing knife is a throwing knife connecting end Y3.
3. The hybrid buck negative resistance converter of claim 2, wherein: when the hybrid negative resistance conversion module inputs negative voltage and the train is in traction working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1The first contact X1 is connected with the throwing knife connecting end X3, and the second mechanical switch K2The first contact Y1 is connected with the throwing knife connecting end Y3; the hybrid buck negative resistance converter outputs a positive polarity specified amplitude voltage between a third connection end (63) and a fourth connection end (64) of the hybrid buck negative resistance converter;
when the hybrid negative resistance conversion module inputs negative voltage and the train is in the regenerative braking working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1A second contact X2 connected to the throwing-knife connecting end X3, and a second mechanical switch K2The second contact Y2 is connected with the throwing knife connecting end Y3; the hybrid buck negative-resistance converter outputs a negative polarity specified amplitude voltage between a third connection end (63) and a fourth connection end (64) of the hybrid buck negative-resistance converter;
when the hybrid negative resistance conversion module inputs positive voltage and the train is in traction working condition, the switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1The first contact X1 is connected with the throwing knife connecting end X3, and the second mechanical switch K2The first contact Y1 is connected with the throwing knife connecting end Y3; the hybrid buck negative resistance converter outputs a positive polarity specified amplitude voltage between a third connection end (63) and a fourth connection end (64) of the hybrid buck negative resistance converter;
when the mixed negative resistance conversion module inputs positive voltage and when the train is in the state of being driven againIn the case of braking operation, switch S1Performing pulse modulation according to the negative resistance characteristic; first mechanical switch K1A second contact X2 connected to the throwing-knife connecting end X3, and a second mechanical switch K2The second contact Y2 is connected with the throwing knife connecting end Y3; the hybrid buck negative-resistance converter outputs a negative polarity specified amplitude voltage between a third connection terminal (63) and a fourth connection terminal (64) thereof.
4. The hybrid buck negative resistance converter of claim 3, wherein: when the buck converter module outputs a negative voltage,
the buck conversion module comprises: input capacitance C1An output capacitor C2A switch S, an inductor L and a freewheeling diode D;
the input capacitor C1A negative terminal and a second connection terminal (62), one terminal of an inductor L, an input capacitor C2The positive end and the sixth connecting end (66) are connected;
the input capacitor C1The positive end of the switch S is connected with the first connecting end (61) and the positive end of the switch S;
the negative end of the switch S is connected with the other end of the inductor L and the cathode end of the freewheeling diode D;
an anode end of the freewheeling diode D, a fifth connecting end (65) and an output capacitor C2The negative ends of the anode and the cathode are connected;
the switch S performs pulse modulation according to the input voltage characteristic;
when the buck converter module outputs a positive voltage,
the buck conversion module comprises: input capacitance C1An output capacitor C2A switch S, an inductor L and a freewheeling diode D;
the input capacitor C1A negative terminal and a second connection terminal (62), an anode terminal of the freewheeling diode D, an output capacitor C2The negative end and the sixth connecting end (66) are connected;
the input capacitor C1The positive end of the switch S is connected with the first connecting end (61) and the positive end of the switch S;
the negative end of the switch S is connected with one end of the inductor L and the cathode end of the freewheeling diode D;
the other end of the inductor L, a fifth connecting end (65) and an input capacitor C2The positive terminals are all connected;
the switch S is pulse modulated according to the input voltage characteristics.
5. The hybrid buck negative resistance converter of claim 4, wherein: the hybrid negative resistance transform module further comprises: an RC absorption circuit;
the RC absorption circuit includes: two absorption resistors Rs1Two absorption resistors Rs2Two absorption capacitors Cs1And two absorption capacitors Cs2；
The first mechanical switch K1First contact X1 and absorption resistor Rs1Is connected to the absorption resistor Rs1Another terminal of (1) and an absorption capacitor Cs1Is connected to the absorption capacitor Cs1Another terminal of (1) and an absorption capacitor Cs2One end of, the first mechanical switch K1The throwing knives are connected with X3, and the absorption capacitor Cs2Another end of (1) and an absorption resistor Rs2Is connected to the absorption resistor Rs2The other end of (2) and the first mechanical switch K1To the second contact X2;
the second mechanical switch K2And a first contact Y1 with a further absorption resistor Rs1Is connected to one end of the other absorption resistor Rs1The other end of which is connected to another absorption capacitor Cs1Is connected to one end of the further absorption capacitor Cs1The other end of which is connected to another absorption capacitor Cs2One end of, a second mechanical switch K2The throwing knives are connected with the connecting ends Y3, and the other absorbing capacitor Cs2With the other end of the other absorption resistor Rs2Is connected to one end of the other absorption resistor Rs2And the other end of the first mechanical switch K2Is connected to the second contact Y2.
6. The hybrid buck negative resistance converter of claim 5The device, its characterized in that: when the hybrid negative resistance conversion module inputs a negative voltage, the hybrid negative resistance conversion module further includes: two diodes Ds1And two diodes Ds2；
At the two absorption resistors Rs1Are respectively connected with a diode D in parallels1And a diode Ds1Anode terminal and first mechanical switch K1Is connected to a first contact X1, and a further diode Ds1Anode terminal and second mechanical switch K2Is connected with the first contact Y1;
at the two absorption resistors Rs2Are respectively connected with a diode D in parallels2And a diode Ds2The cathode terminal and the first mechanical switch K1Is connected to a second contact X2, and a further diode Ds2Cathode terminal and second mechanical switch K2To second contact Y2;
when the hybrid negative resistance conversion module inputs a positive voltage, the hybrid negative resistance conversion module further includes: two diodes Ds1And two diodes Ds2；
At the two absorption resistors Rs1Are respectively connected with a diode D in parallels1And a diode Ds1The cathode terminal and the first mechanical switch K1Is connected to a first contact X1, and a further diode Ds1Cathode terminal and second mechanical switch K2Is connected with the first contact Y1;
at the two absorption resistors Rs2Are respectively connected with a diode D in parallels2And a diode Ds2Anode terminal and first mechanical switch K1Is connected to a second contact X2, and a further diode Ds2Anode terminal and second mechanical switch K2To second contact Y2;
the two diodes Ds1Two diodes Ds2And the RC absorption circuit forms an RCD absorption circuit.
7. The hybrid buck negative resistance converter of claim 4, wherein: the hybrid negative resistance transform module further comprises: an RC absorption circuit;
the RC absorption circuit includes: two absorption resistors RsTwo absorption capacitors Cs1And two absorption capacitors Cs2；
The first mechanical switch K1First contact X1 and absorption capacitor Cs1Is connected to the absorption capacitor Cs1Another terminal of (1) and an absorption capacitor Cs2One end of (1), absorption resistance RsAre all connected, the absorption resistor RsThe other end of (2) and the first mechanical switch K1Is connected with the throwing knife connecting end X3, and the absorption capacitor Cs2The other end of (2) and the first mechanical switch K1To the second contact X2;
the second mechanical switch K2First contact Y1 and a further absorption capacitor Cs1Is connected to one end of the further absorption capacitor Cs1The other end of which is connected to another absorption capacitor Cs2One end of (1), the other absorption resistor RsAre all connected, the other absorption resistor RsAnd the other end of the first mechanical switch K2Is connected to the throw-blade connection terminal Y3, and the other absorption capacitor Cs2And the other end of the first mechanical switch K2Is connected to the second contact Y2.
8. The hybrid buck negative resistance converter of claim 6 or 7, wherein: the switch S1And the switch S are power electronic switches with anti-parallel diodes;
the power electronic switch is as follows: a turn-off switching device or a combination of turn-off switching devices;
the turn-off switching device is: IGBT, MOSFET, SiC-MOSFET or IGCT;
the anti-parallel diode and the freewheeling diode D are fast recovery diodes matched with the turn-off switching device;
the first mechanical switch K1And a second mechanical switch K2All are as follows: a mechanical contact switch;
the mechanical contact switch is as follows: single pole double throw mechanical contact switch.
9. A system for reducing the rail potential of a subway train by applying the hybrid buck negative resistance converter as claimed in any one of claims 1 to 8, wherein: the mixed type voltage reduction negative resistance converter is arranged in a traction power supply system to form a system for reducing the rail potential of the subway train, and the system for reducing the rail potential of the subway train comprises: the system comprises two mixed type voltage-reducing negative resistance converters, a plurality of switch units, a contact network (2), a traveling rail (3) and a return line (5);
the two mixed type voltage reduction negative resistance converters are respectively as follows: a first hybrid buck negative resistance converter (6a) and a hybrid buck negative resistance converter (6 b);
the switch units are respectively as follows: a switch unit (7a), a switch unit (7b), …, a switch unit (7 x);
each of the switching units includes: a switching unit first terminal (71) and a switching unit second terminal (72);
a first connecting end (61) of the first mixed type voltage-reducing negative resistance converter (6a) is connected with a traction network connecting end (11) of the direct-current traction substation (1a), and a first connecting end (61) of the second mixed type voltage-reducing negative resistance converter (6b) is connected with a traction network connecting end (11) of the direct-current traction substation (1 b);
a second connecting end (62) of the first hybrid buck negative resistance converter (6a) is connected with a traveling rail connecting end (12) of the direct-current traction substation (1a), and a second connecting end (62) of the second hybrid buck negative resistance converter (6b) is connected with a traveling rail connecting end (12) of the direct-current traction substation (1 b);
a third connecting end (63) of the first hybrid buck negative resistance converter (6a) is also connected with a traveling rail connecting end (12) of the direct-current traction substation (1a), and a third connecting end (63) of the second hybrid buck negative resistance converter (6b) is also connected with the traveling rail connecting end (12) of the direct-current traction substation (1 b);
a fourth connecting end (64) of the first hybrid buck negative resistance converter (6a) is connected with a return line (5), and a fourth connecting end (64) of the second hybrid buck negative resistance converter (6b) is also connected with the return line (5);
a traveling rail connecting end (12) of the direct current traction substation (1a) and a traveling rail connecting end (12) of the direct current traction substation (1b) are both connected with a traveling rail (3);
the traction network connecting end (11) of the direct current traction substation (1a) and the traction network connecting end (11) of the direct current traction substation (1b) are both connected with the contact network (2);
the first terminals (71) of the switching units are connected to the running rail (3), and the second terminals (72) of the switching units are connected to the return line (5).
10. The system for reducing the rail potential of the subway train as claimed in claim 9, wherein: in an urban rail transit system, the mixed type voltage-reducing negative resistance converter, a return line (5) and a plurality of switch units form a zero-resistance return system; through the matching of the switch unit and the adjustment of the impedance of the hybrid voltage-reducing negative resistance converter, the output impedance of the hybrid voltage-reducing negative resistance converter is offset with the impedance of a return line (5) flowing through current, so that a zero-resistance loop is constructed to transfer the train return current.
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